Particle reduction (also known as comminution) is a very old technology, practiced, for example, by the ancients to produce flour from grain by stone wheel grinding. More refined techniques, such as milling, were developed to produce smaller and more regular powders for use in a variety of industrial applications. Milling processes typically use grinding media to crush, or beat, a product material to smaller dimensions. For example, the product material may be provided in the form of a powder having relatively large particles and the milling process may be used to reduce the size of the particles. Mills typically operate by distributing product material around grinding media and rotating to cause collisions between grinding media that fracture product material particles into smaller dimensions.
Particle compositions having extremely small particle sizes (e.g., nanometer-sized and lower) are proving to be useful for many new applications. However, certain conventional milling methods may be limited in their ability to produce such compositions at very small particle sizes and/or with other features related to particle morphology, topology and/or crystallography. Other processes for producing small particles, such as chemical precipitation and sol-gel, have also been utilized. However, precipitation processes may also have some of the above-noted limitations. In addition, precipitation processes may use relatively long processing times and result in high costs.